Pressure carburetor



Dec. 20, 1949 A. w. oRR, JR

PRESSURE GARBURETOR Filed April 20, 1948 A 01T J1:

IN V EN TGR.

Patented Dec. 20, 1949 TED STATES PATENT OFFICE PRESSURE CARBURETORApplication April 20, 1948, Serial No. 22,167

l. Claim.

The objects of this invention are:

(i) To simplify and make more positive the operation of a pressure typecarburetor when the throttle is almost closed.

2) To prevent the discharge of a slug of gasoline which otherwise wouldbe discharged into the inlet manifold every time the engine is started.

(3) To facilitate the prompt restarting of the carburetor after ashutdown.

This case is a continuation in part of my copending applications SerialNo. 689,260 led- August 8, 1946 and Serial No. 717,673 led December 2l,1946.

The drawing shows the preferred form of my invention.

The air enters at I8, flows through the venturi I2, past the throttleIll and past a long narrow slot I5 in the walls of the outlet pasage |40adjacent to the downstream lip of throttle' I4. A valve I8 on thethrottle shaft controls the communication between the fuel passages and22.

Fuel enters at 24 from the fuel pump 26 having a flexible diaphragm |22flexed by the broken link |24. This link is exed by the cam |26".

When the pressure above the diaphragm |22 is excessive a spring |28 iscompressed. Check valves |30 and |32 complete this well known pump. Thispump is of a well known type.

The check valves l and |32 are each pierced with a tiny hole so that ifthe compressed` spring |28 moves the diaphragm |22 after the engine hasstopped, liquid trapped above the diaphram |22 or above the check valve|30 can escape through |34 which is the fuel entrance to the pump.

Fuel flows from. the entrance 24, through the chamber 50, past thethrottle controlled valve I8, along the passage 22 to the chamber 54above the diaphragm 50. (The diaphragm 56 separates the chamber 50 fromthe chamber 54.) This diaphragm 56 is pushed up by the spring 58 whichpushes a diaphragm 60 up and thus raises the cup 52 which engages withthe underside of the diaphragm 56.

A release valve 54 engages with the upper side of the diaphragm 58 andthe lower side of a diaphragm 18 and controls the flow of fuel from thechamber 51| past the valve 63 to the passage 56, down past the valve 68and so out through nozzle 18 to mixture outlet pasage |40. A diaphragm12, loaded by the spring 14, and the air entrance pressure derived fromthe air impact tube 16 presses the Valve 68 onto its seat.

A diaphragm 18 is subjected on its upper face to the pressure in the airentrance I 0 through the impact tube 1S. The chamber 30, above thediaphragm 18, is connected by the passage 82 to the chamber 84 on theright of the diaphragm 'I2'. The chamber 86, beneath the diaphragm 18,is connected through the restriction 38 with the throat of the venturiI2. An inclined air passage 98 connects the narrow vertical slot I6 withthe chamber 86 through the restriction 92. A drain passage 94 isprovided for obvious reasons.

An acceleration pump is provided and is' operated by a link 98 driven bythe throttle lever 98, mounted on the shaft of the throttle valve I4.This pump comprises a piston |00 which is operated by the link 96.

This piston |00 compresses a spring I 02.- Sprng |02 engages with theright hand face of a diaphragm |04. A passage |I0 connects the chamberI|2 located to' the right of the diaphragm |04.

The left hand face of diaphragm |04 displaces fuel from a chamber |00whenever the throttle is opened. Fuel enters and leaves the chamber |05through the restricted passage |08. This restricted passage |08 isconnected to the descending fuel outlet passage 86.-

Fuel economy' is secured by means of the valve |4. This v'al've' |I4` ismounted on the small horizontal diaphragm. H6. Chamber ||8,locatedbelowthis diaphragm IB, is connected to the passage 82 which isconnected through the inclined' passage 16` and with the air entranceI0. The passage- ||9 connects the chamber II'I, located above thediaphragm I Ifir with the main ir passage |40' downstream of thethrottle I4.

A restricted fuel passage |2"| permits fuel to flow into the chamber 541past the Valve I |4,r from the passage |23' when the valve |'I`4 i'sopened. This passage |2| forms a bypass around the passage 52-20 |8-22.

A spring |25 engages with a cup |21 connected to the valve I4 and tendsto open the valve I I4.

Two springs |20 and |22 are arranged under the cup |29 sov as to engagewith the upper side of diaphragm 18. The inner spring |20 is the Wideopen throttle bias spring and is quite light but exerts this lightpressure at all times. The outer spring |22 exerts zero pressure untilthe choke lever cam |24 has been moved an appreciable degree from itsoff position.

When cam |24 is rotated clockwise then the loose spring |22 iscompressed and an additional compression is added to the pressureimposed by the smaller inner spring |20 at all times.

The spring load on the valve 68 is such that a 3 pressure of 2 to 3pounds per square inch across the diaphragm 12 will open the valve 68and compress the spring I4 and allow fuel to discharge from nozzle 1B.

A pressuredifference of 1 to 2 pounds per square inch will lower thediaphragm Bil and compress the spring 58 and permit the valve S3 toopen.

A low speed adjustment is provided and is shown at 45. This adjustmentpermits fuel to flow from passages 2@ to 22 in addition to that whichflows past the fuel throttle valve IS.

Operation When the engine is stopped, 'the spring |23 in the fuel pumpraises diaphragm |22 and tends to maintain fuel flow to the engine untilthe diaphragm |22 reaches its maximum stroke. Fuel would continue toflow through this carburetor because the light biassing spring |25 tendsto I hold valve 53 open and valve 68 will remain open and discharge thisfuel until the fuel pressure drops below 2 or 3 pounds per square inch.However the bleed holes in check valves I3@ and |32 permit the fueldelivered by diaphragm |22 to be returned to the fuel tank throughfitting I3@ after the engine has stopped so that the fuel is notdischarged to the engine manifold. Also when the pressure in chamber 553falls below 1 or 2 pounds per square inch spring 58 moves cup E2 againstdiaphragm 56 and closes valve 63 against the opposition of the lighterspring 12d. If spring 58 and diaphragm Sil were not provided, the valve63 would normally be opened and diaphragm 56 extended to the limit ofits travel by biassing spring i29 after the engine was stopped. Thenwhen the engine was again started diaphragm 5G would, in moving valve 3to near its closed position, push a slug of fuel into the engine throughvalve 6B. Spring 53 thus through diaphragm Sil and cup 62 holdsdiaphragm 5E in the up position and valve 55S at its closed positionwhen there is no fuel pressure in the chamber 5U. This makes closedthrottle starting of the engine possible with a pressure carburetor.

` When the throttle is slightly opened for starting the valve i8 isopened silghtly. This would not provide suilicient fuel in cold weatherso the cam |24 is rotated clockwise. The springs i2@ and |22 arecompressed so that the valve t3 opens to admit sufficient fuel.

After the engine has started and is running the throttle I4 is opened.As the throttle i4 opens the lip of the throttle sweeps over the longnarrow slot I6 and the suction in the outlet |49. which is transmittedthrough the restriction 92, no longer influences the pressure in thechamber 8B. Thereafter the pressure in the chamber 86 Siti is thepressure in the throat of the venturi I2. The pressure in the throat ofthe venturi I2 thereafter opposes the pressure drop through therestriction 52 in the fuel passage in the well known manner. Thefuel/air ratio is thus maintained constant until the throttle I4 isalmost wide open when the valve II4 is opened by the pressuretransmitted through the passage I I9. The opening of the valve I I4 addsfuel sufficient to develop maximum horsepower.

What I claim is:

The combination of a variable stroke fuel pump and a pressure typecarburetor in which there is a moving wall in said pump acting as apiston, positive means for moving said moving wall on its suctionstroke, spring means for moving said moving wall on its pressure stroke,inlet and outlet check valves, small openings acting as a bypasspassages around said check valves, an air entrance to said carburetor, aventuri therein, a second moving wall responsive to the pressure drop insaid Venturi, a fuel passage leading from said fuel pump, a restrictionin said passage, a third moving wall responsive to the pressure drop dueto fuel now through said fuel restriction, said second and third movingwalls being arranged so as to oppose each other, a fuel valve in serieswith said fuel restriction and connected to said second and third movingwalls, a throttle valve downstream from said venturi, a second fuelvalve connected to the air throttle and located in the fuel passage inseries with said fuel restriction, said second valve being normally Wideopen but adapted to restrict the fuel ow when the throttle is movedtowards its idling position, yieldable means maintaining at al1 times apressure on said second moving wall tending to open the first mentionedfuel Valve, a fourth moving wall, yieldable means tending to move saidfourth movable wall in one direction, the pressure from the first movingwall tending to move said fourth moving wall in the opposite direction,said fourth moving wall being adapted to engage with and to close saidfirst mentioned fuel valve when the fuel pump registers `zero pressure,that is, when the variab stroke pump is not operating.

. ANDREW WILLIAM ORR, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 55 2,361,227 Mock Oct. 24, 19442,432,274 Barr Dec. 9, 1947 2,447,791 Barfod Aug. 24, 1948

